Recently, thin film display devices using field emission have been actively developed as light and thin flat-panel display devices which can substitute for conventional CRT (Cathode Ray Tube).
There are a diode structure and a triode structure in field emission devices. The diode structure has a benefit to be easily prepared and to permit high emission area, but need high driving power and has a problem of low luminous efficiency. Therefore, recently, the triode structure has been mainly used.
In the triode structure, in order to easily emit electrons from a field emitter material, an auxiliary electrode such as a gate electrode is formed to be at a distance of dozens nanometer (nm) to several centimeter (cm) from the cathode electrode.
FIG. 1 is a configuration view of the conventional field emission device having the triode structure. Referring to FIG. 1, cathode electrodes 2 are formed on a surface of a rear substrate 1, and emitters 3 made of carbon nanotubes are formed on the upper surfaces of cathode electrodes 2. Gate electrodes 4 are spaced apart from cathode electrodes 2 at a certain distance, and are formed on the rear substrate 1 via insulating layers 5. A front substrate 6, on which a fluorescent layer 7 and an anode electrode 8 are formed, is formed to be opposite to the rear substrate 1. The anode voltage and the gate voltage for driving the field emission device are supplied by a DC inverter 9 and an AC inverter 10, respectively.
FIG. 2 represents wave shapes of voltage being applied to the anode electrode 8 and the gate electrode 4 in the conventional field emission device with the triode structure. Electrons are emitted from the emitters 3 with an AC voltage applied to the gate electrode 4, and the emitted electrons are accelerated with high DC voltage applied to the anode electrode 8 to excite and radiate fluorescent material 7.
At this time, an AC voltage is applied to the gate electrode 4, while a DC voltage with high value is continuously applied to the anode electrode 8. Therefore, there is a problem that unnecessary power is consumed and a life time of the field emission device is reduced due to application of high voltage for a long time. Moreover, there is a problem that unnecessary electrons are emitted from emitters 3 with high anode voltage.